To download the grass you have to follow the link to the Epic Games forums, and use the link provided by the author. Since it is a share from Google Drive, I recommend you to get it as soon as possible. Only the author has control over both link and content, and at any moment he can either remove or change them.

The model is a small patch of grass that you can replicate over a surface to create a realistic looking environment. It works perfectly for animations and cinematic cameras.

Just keep in mind that using that kind of resource will result in a drop on framerates for your project.